A. Field of the Invention
This invention relates to a method of treating a permeable subterranean formation using water soluble organic polymers which are noncationic in character in a liquid media having a pH of 7 or above in order to stabilize in the formation migrating fines such as silica, iron minerals and alkaline earth metal carbonates.
B. Description of the Prior Art
The recovery of fluids such as oil and/or gas has been troublesome in areas wherein the subterranean formation is composed of one or more layers or zones which contain migrating fines such as silica, iron minerals, and alkaline earth metal carbonates. These fines tend to move or migrate to the well bore during the recovery of formation fluids from the particular layers or zones and frequently the migrating fine block the passageways leading to the well bore. Plugging or materially impairing the flow formation fluids towards the well bore results in a loss of these fluids to the producer or so decreases the rate of hydrocarbon recovery from the well as to cause the well to be shut down because it is economically unattractive to produce therefrom. An additional adverse factor resulting from the movement of the fines towards the well bore is that they are often carried along with the formation fluids to the well bore and pass through the pipes, pumps, etc., being used to recover the formation fluids to the surface with resulting damage to the moving parts thereof as the fines are very abrasive.
Secondary and tertiary methods of recovering hydrocarbons from a subterranean formation are well known. In general, such a method involves introducing a fluid, such as water, steam, etc., into one or more injection wells which penetrate the formation and forcing the fluid toward one or more offset production wells. Migrating fine particles during such an operation can cause a decrease of the rate in which fluid can be injected into the formation and can decrease the permeability or porosity of the formation which results in a decrease in the rate of hydrocarbon production at the offset production wells.
Migrating fine particles are frequently encountered during acidizing or fracturing operations and during sand consolidation operations. The presence of migrating fine particles during these operations can result in a decrease in the permeability of the formation which is being treated.
Gravel packing is a widely practiced method of preventing the production of sand from poorly consolidated formations. The migration of fine particles into the gravel pack can greatly reduce the permeability of the gravel pack. This can result in a decrease in the rate of production of hydrocarbons from the formation.
Consequently, in efforts to overcome these problems, various methods have been developed for treating a subterranean formation in order to stabilize portions in the formation containing migrating fines. For instance, U.S. Pat. Nos. 4,366,071; 4,366,072; 4,366,073; 4,366,074; and 4,374,739 disclose the use of organic polycationic polymers to prevent or reduce the ill effects of swelling clays and/or migrating fines in subterranean formations. These patents are assigned to the assignee of the present of invention and are hereby incorporated by reference.
Organic polycationic polymers have become widely used in preventing permeability damage due to swelling clays and/or migrating fines which are contained within the subterranean formation. These organic polycationic polymers, however, can form precipitates when they come into contact with anionic chemicals such as anionic surfactants and other anionic chemicals used in hydrocarbon recovery. In the past, this problem has been reduced by using chemicals with the organic polycationic polymers which are nonionic or cationic in character in a liquid media. The use of these chemicals, however, can result in higher costs and/or reduced hydrocarbon recovery from a subterranean formation.
The present invention provides a method of stabilizing fines within a subterranean formation using an organic copolymer which overcomes or at least mitigates the above-described problems.